What software do I need to convert a real picture into camera ready art?

Lets say I had a scanned image of any object. What software could I use to convert it into a more simple image, similar to 'clip art'?What software do I need to convert a real picture into camera ready art?hmm, if you can find a free download for Photoshop Cs3 it's golden for anything, the download you can probably find on www.megaupload.com theirs no virus's i promise you, i did it and my laptop works completely fine. Hope this helps.